This invention relates to a disposable pull-on undergarment which absorbs and retains excrements.
Japanese Patent Application Publication No. 1995-236650A discloses a disposable pull-on diaper which comprises a liquid pervious top sheet, a liquid impervious back sheet and an liquid absorbent core interposed between those two sheets, with respective longitudinal side edges of front and rear waist-encircling regions being secured to each other to provide a waist-encircling opening and a pair of leg-encircling openings. In the front waist-encircling region, a plurality of waist elastic members are secured in an extended condition to an edge portion of the waist-encircling opening to extend in a waist-encircling direction. In an edge portion of each leg-encircling opening, a plurality of leg elastic members are secured in an extended condition to extend in a leg-encircling direction. Also, a plurality of auxiliary elastic members are secured in a location intermediate between the waist elastic members and the leg-encircling opening edge portions to extend in the waist-encircling direction between the longitudinal side edges of the front and rear waist regions.
Each auxiliary elastic member has an extensible portion and a non-extensible portion. The extensible portion extends from longitudinal side edges of the core positioned over the front and rear waist-encircling regions toward respective longitudinal side edges of the front waist-encircling region. The non-extensible portion traverses the core to extend between opposite longitudinal side edges of the core. The extensible portions of the auxiliary elastic members act to squeeze a wearer's waist so that the diaper while in use is prevented from sliding down from its position. In the non-extensible portions of the auxiliary elastic members, the diaper is not subjected to an extension stress from the auxiliary elastic members which may otherwise cause the core to contract, so that the core is prevented from puckering.
The diaper disclosed in the above-identified reference relies solely on the extensible portions of auxiliary elastic members to prevent its downward slide and accordingly needs to increase an extension stress of the auxiliary elastic members in their extensible portions. Such a diaper thus squeezes a wearer's waist in a severe manner and provides discomfort to a wearer of the diaper. The non-extensible portions of auxiliary elastic members do not act to press the core against a wearer's skin. This increase a tendency of the core to be spaced away from the wearer's skin during the use of the diaper, and accordingly hinders an excrement-absorbing function of the core.